The reforming of petroleum hydrocarbon streams is one of the important petroleum refining processes that may be employed to provide high-octane number hydrocarbon blending components for gasoline. In the typical reforming process, the reactions comprise dehydrogenation reactions, isomerization reactions, and hydrocracking reactions. The dehydrogenation reactions include the dehydrogenation of cyclohexanes to aromatics, the dehydroisomerization of alkylcyclopentanes to aromatics, the dehydrogenation of paraffins to olefins, and the dehydrocyclization of paraffins and olefins to aromatics. The isomerization reactions include isomerization of n-paraffins to isoparaffins, the hydroisomerization of olefins to isoparaffins, the isomerization of alkylcyclopentanes to cyclohexanes, and the isomerization of substituted aromatics. The hydrocracking reactions include hydrocracking of paraffins and hydrodesulfurization. Adequate discussions of the reactions occurring in a reforming reaction zone are presented in CATALYSIS, Vol. VI, P. H. Emmett, editor, Reinhold Publishing Corporation, 1958, pages 497-498, and PETROLEUM PROCESSING, R. J. Hengstebeck, McGraw-Hill Book Company, Inc., 1959, pages 179-184.
It is well-known by those skilled in the art that several catalysts are capable of reforming petroleum naphthas and hydrocarbons that boil in the gasoline boiling range. Although reforming may be carried out through the use of molybdena-on-alumina catalysts, chromium-oxides-on-alumina catalysts, platinum-halogen-on-alumina catalysts, and platinum-aluminosilicate-material-alumina catalysts, the catalysts employing platinum as a hydrogenation component are generally employed today in the reforming processes of the petroleum industry.
It is known by those skilled in the art that gallium can be used to promote a platinum-containing reforming catalyst. In U.S. Pat. No. 2,814,599, Lefrancois, et al., teach that a platinum-containing reforming catalyst can be promoted with a small amount of gallium. In U.S. Pat. Nos. 3,772,183 and 3,772,184, Bertolacini, et al., disclose reforming processes employing two catalysts. In each case, the first catalyst in the system can be a catalyst that comprises a platinum-group-metal hydrogenating component, a halide, and optionally a small amount of rhenium on a catalytically-active alumina. In U.S. Pat. No. 3,772,183, an embodiment of the second catalyst comprises a Group VIII noble metal, about 0.05 to 3 wt% gallium, and optionally a halide on a solid catalytic support, particularly catalytically-active alumina. In U.S. Pat. No. 3,772,184, an embodiment of the second catalyst comprises a Group VIII noble metal as a hydrogenating component, about 0.05 wt% to about 3 wt% rhenium, about 0.05 wt% to about 3 wt% gallium, and optionally a halide on a porous refractory inorganic oxide, particularly catalytically-active alumina. In addition, Bertolacini, et al., in U.S. Pat. No. 3,772,184, teach a single-catalyst reforming process which employs as its catalyst the second catalyst of the above-described two-catalyst system of that reference. In U.S. Pat. No. 4,325,808, Kim, et al., disclose a catalyst system comprising a physical particle-form mixture of two catalysts, the first catalyst comprising at least one noble metal component, preferably platinum, and a combined halogen on a refractory inorganic oxide and being free of a crystalline aluminosilicate component, and the second catalyst being free of a noble metal and comprising at least one metal component deposed on a solid support comprising a crystalline aluminosilicate material dispersed in a refractory inorganic oxide. The metal of the second catalyst of this system can be gallium or rhenium. In U.S. Pat. No. 4,048,249, Antos discloses a multimetallic catalytic composition comprising a combination of catalytically-effective amounts of a platinum group component, a gallium component, a cobalt component, and a halogen component on a porous carrier material. Antos discloses further that the catalyst of his invention is suitable for the dehydrocyclization of dehydrocyclizable hydrocarbons and that particularly good results are obtained when the catalyst is prepared and maintained during use in a substantially sulfur-free state. Of course, in such case, the use would be conducted in a substantially sulfur-free environment.
Now there has been found a reforming catalyst containing a Group VIII noble metal, a Group VIII non-noble metal, and gallium on separate support particles, which catalyst provides superior performance when it is used for the reforming of a feedstock containing sulfur.